(a) Technical Field
The present invention relates to a system and method for improving a steering feeling in a neutral gear position of a vehicle, and more particularly, to a method for improving a steering feeling of a vehicle when the vehicle travels in a neutral gear mode through an operation of an eco-roll system.
(b) Background Art
In general, a vehicle includes power steering apparatuses for reducing a steering power of a driver during a steering operation. The power steering apparatuses include hydraulic power steering apparatuses for assisting a steering power using a hydraulic pressure formed by a hydraulic pump, and electric power steering apparatuses for assisting a steering power using a driving torque (e.g., rotating power) of an electric motor.
Moreover, the hydraulic steering apparatuses using a hydraulic pump (e.g., power steering pump) are widely used in commercial vehicles such as large-sized vehicle, and the hydraulic pump receives a rotating power of an engine to be driven. Furthermore, as a system mainly applied to a commercial vehicle, an eco-roll system is operated when a driver disengages an accelerator pedal while the vehicle travels at a predetermined speed (i.e., 50 km/h) or higher.
FIG. 1 is an exemplary view showing an operation condition of an eco-roll system. The eco-roll system is a system in which a control unit is configured to automatically change a gear state of a transmission into a neutral (N) gear while the gears of the transmission are engaged without a separate driver manipulation when a speed of the vehicle is a predetermined speed or higher during a downhill travel of the vehicle.
After conversion into a neutral gear state, as shown in FIG. 2, the eco-roll system lowers an engine RPM to an idle state, and an inertial travel is made by the inertia of the vehicle in an idle state, thereby improving a fuel ratio of the vehicle (e.g., the fuel ratio is improved by reducing a rolling resistance of the vehicle).
Referring to FIG. 1, when an accelerator pedal is disengaged for a predetermined time or longer at a predetermined speed or higher, an eco-roll mode is performed. Referring to FIG. 2, an idle RPM is maintained at the same time when the gear of the vehicle is converted into a neutral gear state during an operation of the eco-roll mode.
However, when an eco-roll mode for improving fuel ratio is operated, an engine RPM is lowered to an idle state, and an output of a power steering pump that receives a rotating power of an engine to be driven is also lowered at the same time. Accordingly, a driver needs to apply a stronger force to manipulate steering power, and may experience a sudden heavy feeling of a steering wheel or a kickback phenomenon.